An ex-convict accused of killing his two children and two older stepchildren at his suburban Detroit home will undergo a mental competency evaluation.

The exam will put Gregory V. Green's case on hold, likely for weeks. He appeared in a Dearborn Heights court Wednesday, two weeks after two kids died from carbon monoxide poisoning and two teens were fatally shot.

Police say Green killed the teen stepchildren in front of their mother, who is also his wife, and then called 911. He's charged with first-degree murder, assault and torture. Green's wife, Faith Green, survived, despite being attacked with a box cutter and shot.

Gregory Green was released from prison in 2008 after serving 16 years for killing his pregnant first wife. He had pleaded no contest to second-degree murder.